1. Field of the Invention
The present invention relates to the field of power management. More specifically, the present invention relates to the field of local and global power management in a programmable analog circuit.
2. Related Art
A microcontroller is a highly integrated chip having all or most of the necessary components to control some process or aspect in a circuit. For example, the microcontroller typically includes a central processing unit (CPU), random access memory (RAM), read only memory (ROM), input/output (I/O) interfaces, timers, and interrupt controller. The typical microcontroller has bit manipulation instructions, easy and direct access to I/O interfaces, and quick and efficient interrupt processing. By including only features specific to the task of the microcontroller and integrating the functionality onto a single chip, the cost to produce the microcontroller can be drastically reduced.
Programmable analog circuit designs for microcontrollers allow a user limited programmability to vary circuit parameters or the underlying topology of the programmable analog circuit. For example, a programmable analog circuit may be comprised of interconnected analog blocks set in a fixed topology that has programmable parameters, such as filter bandwidth or roll-off, that can be set and changed according to application needs. While the signal processing path and basic functionality of the analog circuit remains unchanged, some programmable functionality is introduced by letting parameters vary in the programmable analog circuit.
A particular functionality important to programmable analog circuit designs is power management. Power management is particularly important in light of the movement towards lower voltage levels needed to accommodate the ever decreasing size of circuit components. As end products become more lightweight, smaller, and more portable, the requirement for three volt and lower microcontrollers allows for less power consumption and longer battery life. However, in the past, designing the proper analog circuitry for lower power consumption was difficult to achieve without sacrificing operating performance. As a result, microcontrollers previously offered limited power management functionality.
Previous methods for controlling power using analog circuits reduced the overall performance capabilities of the programmable circuit. Programmable analog circuit blocks include basic programmable operational amplifier circuits used for many functionalities including gain amplifiers, switch capacitor integrators, analog to digital (A/D) converters, digital to analog (D/A) converters, filters, etc. In addition, a switched capacitor integrator forms the basis for an analog processing unit that can support A/D and D/A digital converters, comparators, programmable gain amplifiers, and filters.
One method implemented in the past for controlling power management throughout a programmable analog circuit included increasing or decreasing the bias voltage. The bias voltage drives the operational amplifier in the programmable analog circuit. Increasing the bias supply voltage does increase the speed of the operational amplifier and the overall circuit; however, the improvement comes at a cost of performance.
Increasing the bias voltage increases the current through the operational amplifier in the programmable analog circuit. More current increases the slew rate of the circuit and increases the circuits ability to overcome the load capacitance in the circuit. This allows the operational amplifier to run faster resulting in better performance.
However, there is a tradeoff. By increasing the bias voltage, the dynamic range of the operational amplifier is reduced. Basically, the dynamic range of the output voltage is clipped or reduced for the analog circuit containing the operational amplifier. As a result, increasing the bias voltage negatively decreases the dynamic range of the circuit containing the operational amplifier.
Conversely, to maintain the dynamic range, the bias voltage must be reduced. However, at low bias levels (and hence lower supply voltages, such as, three volts), the circuit containing the operational amplifier operates at much slower speeds.
Thus, a need exists to provide a degree of programmability to power management in a programmable analog circuit. Another need exists to provide increased speeds in a programmable analog circuit without sacrificing performance.
The present invention discloses a method and system for power management in a programmable analog circuit. The present invention provides for a degree of programmability in the management of power in a programmable analog circuit. Also, the present invention meets the above need and provides for increased speeds in a programmable analog circuit without sacrificing performance.
These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments which are illustrated in the various drawing figures.
The present invention discloses a method and system for local and global power management in a programmable analog circuit. Specifically, one embodiment of the present invention describes an array of programmable analog circuit blocks, wherein each block contains an operational amplifier circuit component. In each programmable analog circuit block, there are duplicate current mirror circuits that are coupled in parallel fashion. These current mirrors drive the operational amplifier circuit component in a corresponding analog circuit block. The mirror circuits function to consume more current when enabled, thereby increasing the speed of the operational amplifier component in the analog circuit block.
Global power management is achieved by increasing and decreasing the bias voltage that is applied to each analog circuit block in the array, in accordance with another embodiment of the present invention. Global configuration control bits select between the various bias voltages available. Increasing the bias voltage increases current through the programmable analog circuit blocks. Correspondingly, an increase in speed of the entire circuit is effected.
In another embodiment, the global configuration control bits can select to electrically disable the bias voltage to the array of programmable analog circuit blocks. Switches selected by the global configuration control bits either provide a bias voltage to each of the programmable analog circuit blocks, or quickly disable the analog block.
Local power management is provided by enabling or disabling mirror circuits with switches controlled by local configuration control bits to adjust the performance in a corresponding operational amplifier circuit contained within a programmable analog circuit block, in accordance with one embodiment of the present invention.
A microcontroller controls the global management of power through the programmable analog circuit. The same or separate microcontroller controls local management of power through each of the operational amplifiers in each of the programmable analog circuit blocks.